Piston manufacture



Feb. 16, 1965 w. c. REINBERGER PISTON MANUFACTURE Filed Nov. 27, 1961 2Sheets-Sheet 1 u mm 6 z z b 2 2 3 2 ,H W ll L a z b rm m m z 2 ar E i ma m a 1i 4: E a Q m g i i W 6 M M m 2.. 1 L I v 3 2 2 z 0 a Z 2 m m uINVENTOR. M'l/fam C. ee/nberyer' United States Patent 3,169,638 PISTONMANUFACTURE William C. Reinherger, Independence, Ghio, assign-or toThompson Rama Wooldridge Inc, Cleveland, Ohio, a corporation of OhioFiled Nov. 27, 1961, Ser. No. 155,014 9 Claims. (Cl. 207-) Thisinvention relates to the forging of metal between punch and dieassemblies involving an initial free fiow of the metal to create aplastic metal mass which will easily flow between the punch and die forproducing the desired shape without requiring special punch and diecontours to create a uniform advancing front of extruding metal and toprevent galling. More specifically this invention deals with themanufacture of trunk type pistons from cast aluminum slugs by impactextrusion of the metal slug between a die and a punch shaped to form thedesired piston contour and wherein the slug is initially flattened intobiscuit form to cooperate with the die and punch for providing spacesfor free lateral flow of the metal to create a plastic flowing masswhich can easily flow between the die and punch and wherein theadvancing wave of flowing metal between the die and punch is restrictedby a punch shoulder to form the desired end shape on the piston skirt.

Heretofore, impact forging of metal articles between a die and a punchhas required the use of metal preforrns with excess metal massespositioned at areas where flow of metal is difficult. Further, the punchand die configuration could not be dictated alone by the desired shapefor the finished article since contours had to be provided to preventgalling and to assist in the formation of a uniform advancing wave frontof metal between the die and punch. As a result, the blank obtained bysuch prior known techniques had to be machine finished into its desiredend shape or had to be equipped with metal fillets and the like excessmetal areas which are undesirable in the finished article.

The present invention now eliminates the necessity for unevendistribution of metal masses in the preform and for varying the die andpunch shapes from the exact desired contour to produce the finishedarticle. According to this invention, the metal preform need only beshaped so as to center itself in the die and to cooperate with the dieand punch for providing free spaces for initial flow of metal to createa free flowing plastic mass which can easily rise into the space betweenthe punch and die, According to this invention, there is no need forcontrolling the advancing wave front of metal between the punch and diesince the punch is equipped with a flow stopping shoulder or abutmentwhich will level off the advancing wave front of flowing metal and willat the same time shape the end face of the flowing metal into thedesired contour.

A feature of the invention includes the provision of a V slight gapbetween the punch and die beyond the punch shoulder for receiving flashof excess metal thereby providing a safety valve effect which willinsure the supply of sufficient metal to form the complete articlewithout damaging the punch and die in the event an excess of metal ispresent.

Another feature of the invention resides in the control of the flashthickness between the punch and die so that removal of the flash by alathe turning operation will simultaneously turn down the circumferenceof the article to the desired finished shape and size.

Another feature of the invention resides in the endwise impacting ofcast metal slugs to form biscuits which will be self-centering in theextrusion die and will cooperate with the punch and die to providespaces for free lateral flow of metal during the period of initialpiercing of the "ice biscuit by the punch to thereby create a freeflowing plastic mass that can easily rise into the space between thepunch and die. This creation of the free flowing plastic mass of metalmakes possible the use of punch and die shapes which are dictated onlyby the desired shape of the finished article.

Another and still further object of this invention is to provide a newand improved method for manufacturing an internal combustion enginetrunk type piston from a suitable material, such as aluminum alloy,brass, magnesium or low carbon steel.

Other and further objects of the invention will be apparent to thoseskilled in the art from the following detailed description of theannexed sheets of drawings,

which by way of preferred embodiment, illustrate the method andapparatus of this invention.

On the drawings:

FIGURE 1 is a fragmentary vertical section of a die and punch having abillet shown in full and dotted lines disposed in a die cavity;

FIGURE 2 is a fragmentary cross sectional view of a die and a punch withthe punch shown in elevation for shaping the billet into a hollow typepiston;

FIGURE 3 is a fragmentary cross sectional view similar to FIGURE 2 onlywith the billet being shown partially formed as a result of being struckby the punch and with the punch shown in elevation;

FIGURE 4 is a fragmentary cross sectional view similar to FZGURES 2 and3 with the punch shown in elevation, and showing the piston blank formedto shape;

FIGURE 5 is a plan view of the piston blank illustrated in FIGURE 4;

FIGURE 6 is an enlarged fragmentary cross sectional view showing afragment of the piston blank illustrated in FIGURE 4; and

FIGURE 7 is a cross sectional view taken substantially on the lineVII-VII looking in the direction indicated by the arrows, as seen inFIGURE 5, only showing the piston turned down to finished diameter andwith the flash removed.

As shown on the drawings:

In FIGURE 1, a slug it) is illustrated. This slug may be cut from asolid cast aluminum rod (not shown) which rod may also be made fromother suitable materials such as brass, magnesium, or low carbon steel.

In FIGURE 1, an apparatus 11 is illustrated for the purpose of kneadingthe slug to form a biscuit or billet 12. This billet is of a shorterheight and a greater'diameter than the slug as shown by the dotted linesin FIG- URE 1 and the full lines in FIGURE 2. The material used in themanufacture of the slug 16 and the billet 12 may be made from a segmentof either cast or wrought bar stock. Cast material is generallypreferred because it is less expensive than wrought stock. The billet 12has a cylindrical side wall 12a with a flat bottom 12b and a convexdomed top 120.

The apparatus ll for kneading the slug 10 includes a die member 13having a die cavity 14 including a flat die bottom 15 which is disposedat an upper end of billet ejector pin 15'. The apparatus 11 furtherincludes a frusto-conical side wall 16 which is joined at one end withthe flat bottom 15 and at its opposite end with a circular die Wall 17.A slug punch 18 is vertically movable in the die cavity 14 toward diebottom 15 for the purpose of forming the slug 10 into the billet 12.

Before the slug is formed into the billet 12, it is preheated whereuponit is upset by the apparatus 11 to decrease its length and to increaseits radial dimensions, as shown in FIGURE 1. In the operation of theapparatus 11, it will be noted that the cavity 14 of the die thatconfines the slug is shaped to produce a tapered section or end 12d atone end of the billet. The opposite end has a Preferably spherical ordomed surface, as illustrated at 120.

In FIGURES 2-4, an apparatus for forming cup-shaped articles isindicated generally at 23. The apparatus 29 includes a punch 21 and adie 22. The die 22 has a generally cylindrical axially extending diewall 22a as well as a generally radially extending bottom die wall 225.The bottom die wall 221) comprises an upper end surface of a verticallymovable piston ejector 2.3, the piston ejec tor being vertically movableafter the billet 12 is formed into a piston blank 25 in bore 22a toeject the blank 25 from the apparatus 26. The punch 21 is mounted forreciprocation in a die cavity lie in the formation of the piston blank25.

The punch 21 is preferably formed with a domed or spherical surface 215at one end thereof. The punch 21 is further provided with a series ofsuperimposed punch head sections of progressively increasing crosssectional size as identified at 2117, 21c, 21d and 216, the domedsurface Ella being disposed on the lowermost punch head section Zlb.Extending vertically on opposite sides of the punch head sections 21b,21c and 21d are wrist pin forming portions or notches 21 At the juncturebetween the punch head sections 21d and 216, an annular undulated punchshoulder Big is provided which is adapted to axially confront the diecavity bottom 22b.

According to my process, the billet i2 is inserted within the die cavityin such a way that billet surfaces 12:: and 12c are spaced from the dieside wall 22a so that as the punch is driven against the blank or billet12, the blank material is caused to flow from the blank into the spacesaround the billet to create a free flowing mass of plastic material asindicated at 12a, 12b and 12d in FIGURE 3. As the movement of the punchis continued, the plastic billet material is caused to flow between thepunch and die into the punch notches 21f extruding opposed wrist pinboss portions, as shown in FIGURE 4 whereupon the flow of the plasticmaterial is arrested when it abuts against the undulated punch shoulder21g.

It will be appreciated the metal is conditioned as it flows into theannular space between the external surfaces 21a, 21b and 21c and the dieside wall 22a so that the material will more readily flow along thepunch 21 as it continues its stroke (FEGURE 3).

In establishing proper flow of the metal it is important that asuflicient space he provided to allow the metal to start to flow beforeit is required to fill the relatively thin shaping piston cavity betweenthe punch and the die, such as between the punch surface 211! and thedie side wall 22?. This initial unrestricted'flow of the metal makes itpossible to use cast stock or to use metal that otherwise could not beextruded by this process.

By practicing the process described above, it is possible to produce thepiston blank or cup-shaped blank 25 as shown in FTGURES 4, and 6. Thepiston blank or cup-shaped blank has a piston head 25a with a dependingring flange 25b and a center skirt 25c. Wrist pin bosses 25d, 25:!extend from the 25a axially along ring flange b and skirt 15c andterminate at the open end of the skirt. The pin bosses are thicker thanthe skirt and ring flange.

1n the practice of my method, as the metal in the billet is displaced bythe forward motion of the punch 21, it flows unrestricted into a narrowspace or die flash cavity 26 between the punch and die untilthe fastermoving metal reaches the shoulder on the punch. The other spaces wherethe metal is moving more slowly will then fill out to the desired len thand any excess metal that may have been contained in the billet 12 canextrucle out through the narrow space or die flash cavity 26 (FIG- URE4) between the punch and the die surface 22a as flash 25s to preventdamage to the punch and die. After the piston blank 25 is removed fromthe die cavity by Operation of the ejector 23, the flash is thenremoved. The flash 254: that is extruded out through the narrow space 26can be removed by the machine or lathe turning operation that reducesthe piston to finished diameter as indicated by the trim line 27 inFIGURE 6. Thus the flash thickness is the same as the thickness of themetal that must be removed to reduce the piston to finished iameter.Therefore flash removal and trimming the piston to size are accomplishedby the same operation to form the finished cup-shaped article or trunktype hollow piston 23 (FIGURE 7). a The piston 28 may be furtherprocessed by cutting piston ring grooves in the ring flange 25b bydrilling wrist pin holes in the pin bosses, in a conventional manner asis Well known in this art.

The impact forging operations of this invention are preferably carriedout at elevated temperatures best suited for the particular metal beingforged. In the case of high silicon aluminum alloy containing around 16%silicon forging temperatures of from 750 to 950 F. are used.

This process therefore produces a piston of the type with a skirt ofvarying length without special machining operations to produce thedesired configuration at the open end. It is capable of producingpistons with essentially no draft or taper on either internal orexternal surfaces. By this method, pistons may be extruded withoutcompromising the optimum internal or external configuration to controlthe flow of metal during the forging process.

It will be understood that modifications and variations may be effectedwithout departing from the scope of the novel concepts of the presentinvention.

1 claim as my invention:

1. The method of making a cup-shaped article which comprises endwiseimpacting a metal slug to form a flattened-biscuit with a dome top and atapered bottom, inserting the biscuit in a die sized to position theapex of the dome top at the axial center of the die and to provide aspace surrounding the tapered bottom, inserting a punch in the diehaving a side wall spaced from the die, a nose initially engaging theapex of the dome top of the biscuit'in the die and a shoulder forlimiting flow of biscuit metal between the punch and die, forcing thepunch into the biscuit to initially flow biscuit metal laterally intothe spaces between the punch and die provided by the dome biscuit topand the tapered biscuit bottom to thereby plasticize the metal,continuing the forcing of the punch into the biscuit to flow the plasticmetal between the punch and die and against the shoulder of the punch,and extruding flash metal of controlled thickness beyond the shoulder ofthe punch to accommodate excess biscuit metal without damaging the punchand die.

2. The method of making die forged pistons from slugs which comprisesthe steps of heating a cylindrical slug to forging temperatures, forgingsaid slug endwise to decrease the height and increase the diameterthereof and simultaneously to form on one end thereof a domed contourand on an opposite end thereof a tapered contour, centering theresulting billet in a die to cooperate therewith in forming spacesbetween them for free flow of metal, causing the billet to be forgedaround a punch initially flowing metal from the billet into the spacesaround the billet to create a free flowing mass of plastic material,continuing to punch the billet causing the plastic material to flowbetween the punch and die extruding opposed wrist pin boss portions andthen arresting the flow of metal against a shoulder on the punch to forma skirt, allowing excess billet metal comprising flash to flow axiallypast said shoulder radially outwardly of said shoulder between the punchand die, and controlling the thickness of the flash so that saidthickness is equal to or less than the depth of a cut to be made duringsubsequent turning of the piston.

3. The method of making die forged pistons from slugs which comprisesthe steps of heating a cylindrical slug to forging temperatures, forgingsaid slug endwise to decrease the height and increase the diameterthereof forming one end with a domed contour and an opposite end with abeveled contour, centering the resulting billet in a die leaving spacesbetween them for free flow of metal, causing the billet to be forgedaround a punch initially flowing metal from the billet laterally intothe spaces around the billet to create a free flowing mass of plasticmaterial, continuing to punch the billet causing the plastic material toflow between the punch and die extruding opposed wrist pin boss portionsand then arresting the flow of metal against a shoulder on the punchforming a cylindrical skirt and forming an end of the skirt at the openend 'of the piston blank to final shape, and allowing excess billetmetal to flow axially past said shoulder radially outwardly of saidshoulder between the punch and die.

4. The method of making die forged pistons from slugs which comprisesthe steps of heating a cylindrical slug to forging temperatures, forgingsaid slug endwise to decrease the height and increase the diameterthereof forming one end with a domed contour and an opposite end with abeveled contour, centering the resulting billet in a die leaving spacesbetween them for free flow of metal, causing the billet to be forgedaround a punch initially flowing metal from the billet laterally intothe spaces around the billet to create a free flowing mass of plasticmaterial, continuing to punch the billet causing the plastic material toflow between the punch and die extruding opposed wrist pin boss portionsand then arresting the flow of metal against a shoulder on the punchforming a cylindrical skirt and forming an end of the skirt at the openend of the piston blank to final shape while allowing excess billetmetal to flow axially past said shoulder radially outwardly of saidshoulder between the punch and die, arresting the flow of metalinitially against portions of a shoulder axially opposite the wrist pinboss portions with the metal then being flowed to fill out the diebetween the wrist pin portions and allowing excess billet metal to flowamally past and radially outwardly of the shoulder with the piston blankbeing thereby formed with an annular undulated shoulder at its open endwith portions of the shoulders extending axially beyond the bosses to agreater extent circumferentially between the bosses as opposed toportions of the shoulder axially opposite the bosses.

5. An apparatus for manufacturing cup-shaped forged piston blanks havingexcess flash located along its outside diameter comprising a die and aforging punch mounted for reciprocation in a die cavity defined by thedie, the punch having a series of axially related sections ofprogressively increasing diameter for movement of metal in said diecavity and with an annular undulated shoulder disposed at a lowermostend of the uppermost of said sections, the punch havingcircumferentially spaced Wrist pin recesses extending axially in saidsections terminating axially below said undulated shoulder, theuppermost of said sections having a diameter slightly smaller than saiddie cavity providing a flash cavity therebetween permitting excessbillet material to be extruded axially of said punch shoulder as abillet is forged by said punch.

6. An apparatus for manufacturing cup-shaped forged piston blanks havingexcess flash located along its outside diameter comprising a die and aforging punch mounted for reciprocation in a die cavity defined by thedie, the punch having a series of axially related sections ofprogressively increasing diameter for movement of metal in said diecavity and with an annular undulated shoulder disposed at a lowermostend of the uppermost of said sections, the punch havingcircumferentially spaced wrist pin recesses extending axially in saidsections terminating axially below said undulated shoulder, theuppermost of said sections having a diameter slightly smaller than saiddie cavity providing a flash cavity therebetween permitting excessbillet material to be extruded axially of said punch shoulder asa billetis forged by said punch, said undulated shoulder having lower shoulderportions disposed in close adjacency to said wrist pin notches andhaving other shoulder portions spaced axially from the wrist pin notchesa greater distance than said lower shoulder portions for forming acup-shaped piston blank with an undulated piston blank shoulder at itsopen end.

7. An apparatus for manufacturing cup-shaped articles having excessflash located along its outside diameter comprising a die and a forgingpunch mounted for reciprocaticn in a die cavity defined by the die, thepunch having a series of axially related sections of progressivelyincreasing diameter for moving metal insaid die cavity and with anannular shoulder disposed at a lowermost end of the uppermost of saidsections, the uppermost of said sections having a diameter slightlysmaller than said die cavity providing a hash cavity therebetweenpermitting excess billet material to be extruded axially of said punchshoulder as a billet is forged by said punch said shoulder having anannular undulated conformation corresponding to a shape to be impartedto an axial shoulder of a center skirt on a cup-shaped piston blank.

8. The method of making die forged pistons from slugs which comprisesthe steps of heating a cylindrical slug to forging temperatures, forgingsaid slug endwise to decrease the height and increase the diameterthereof, centering the resulting billet in a die to cooperate therewithin forming spaces between them for free flow of metal, causing thebillet to be forged around a punch initially kowing metal from thebillet into the spaces around the billet to create a free flowing massof plastic material, continuing to punch the billet causing the plasticmaterial to flow between the punch and die extruding opposed wrist pinboss portions and then arresting the flow of metal against a shoulder onthe punch to form a skirt, allowing excess billet metal comprising flashto flow axially past said shoulder radially outwardly of said shoulderbetween the punch and die, and controlling the thickness of the flash sothat said thickness is equal to or less than the depth of a cut to bemade during subsequent turning of the piston.

9. The method of making die forged pistons from slugs which comprisesthe steps of heating a cylindrical slug to forging temperatures, forgingsaid slug endwise to decrease the height and increase the diameterthereof to form a billet, centering the billet in a die with the outerwalls of the billet being spaced radially inwardly from the die walls toprovide free space between the die and the billet, inserting a punch inthe die with the side wall of the punch being spaced a predetermineddistance from the die and having a nose initially engaging one end ofthe billet in a die and a shoulder for limiting the flow of billet metalbetween the punch and the die, punching the billet and initiallyradially flowing metal from the billet into the free space around thebillet to create a free flowing mass of plastic material, continuing topunch the billet and causing the plastic material to flow between thepunch and die extruding opposed wrist pin boss portions, and arrestingthe flow of metal against a shoulder on the punch to form a skirt.

References Qited in the file of this patent UNITED STATES PATENTS1,720,722 Dean July 16, 1927 2,360,354 Lyon Oct. 17, 1944 2,679,931Cigliano June 1, 1954 2,740,519 Sparks Apr. 3, 1956 2,795,467 ColwellJune 11, 1957 FOREIGN PATENTS 94,882 Switzerland June 1, 1922

1. THE METHOD OF MAKING A CUP-SHAPED ARTICLE WHICH COMPRISES ENDWISEIMPACTING A METAL SLUG TO FORM A FLATTENED BISCUIT WITH A DOME TOP AND ATAPERED BOTTOM, INSERTING THE BISCUIT IN A DIE SIZED TO POSITION TH APEXOF THE DOME TOP AT THE AXIAL CENTER OF THE DIE AND TO PROVIDE A SPACESURROUNDING THE TAPERED BOTTOM, INSERTING A PUNCH IN THE DIE HAVING ASIDE WALL SPACED FROM THE DIE, A NOSE INITIALLY ENGAGING THE APEX OF THEDOME TOP OF THE BISCUIT IN THE DIE AND A SHOULDER FOR LIMITING FLOW OFBISCUIT METAL BETWEEN THE PUNCH AND DIE, FORCING THE PUNCH INTO THEBISCUIT TO INITIALLY FLOW BISCUIT METAL LATERALLY INTO THE SPACESBETWEEN THE PUNCH AND DIE PROVIDED BY THE DOME BISCUIT TOP AND TAPEREDBISCUIT BOTTOM TO THEREBY PASTICIZE THE METAL, CONTINUING THE FORCING OFTHE PUNCH INTO THE BISCUIT TO FLOW THE PLASTIC METAL BETWEEN THE PUNCHAND DIE AND AGAINST THE SOULDER OF THE PUNCH, AND EXTRUDING FLASH METALOF CONTROLLED THICKNESS BEYOND THE SHOULDER OF THE PUNCH TO ACCOMMODATEEXCESS BISCUIT METAL WITHOUT DAMAGING THE PUNCH AND DIE.